Annealing leer or furnace



R. D. PIKE ANNEALING LEER OR FURNACE March 11 19.24. 1,486,265

Filed-Oct. 25. 1922 4 Sheets-Sheet 1 INVENTOR.

ANNEALING LEER OR FURNAGB Filed Oct. 25 1922 4 Sheets-Sheet 2 I N VENTOR.

TTO NE March `11 1924. 1,486,265

K R. D. PIKE ANNEALING LEER 0R FURNAE Filed Oct. 25 1922 4 Sheets-Sheet3 HVVENTOR.

R. D. PIKE ANNEALING LEER on FURNACE March 11 1924.

Filed Oct. 25 1922 4 Sheets-Sheet 4 Maz' l 71TH 12W fo mf'ple Byvqfforneffs Patented Mar. 1,1, 1924.

UNITED STATES PATENT on-Ica ROBERT,` D. PIKE, 0F SAN FRANCISCO,`CALIFORNIA.

ANNEALING LEER OR FURNACE.

Application med october 25, 1922. serial NQ. 596,732.

-of the continuously operated type in which the glassbottles orotherarticles are passed more or less continuously through a -hori- Zonta]muflle or tunnel composed of refractory material; and during suchpassage are subjected to a more or less predetermined sequence oftemperature to accomplish z the process known as annealing. It is mostusual in modernpractice to impart the necessary temperature to the glassarticles by causing to circulate in suitably Vde si,g;ned dues aroundthe outside of the mule,'hot gases of combustion. These are usuallyhottest near the front end of the leer where the articles enter, theylsame being raised as quickly as possible to the desired maximumannealing temperature and then being allowed to slowly lcool during theremainder of the passage through the muiile. This method of annealing iseconomical because the fuel employed is relatively cheap, but onlyproduces` indifferent results in respect of uniformly removing theinternal stress of the glass. This is because, in order to entirelyremove these internal stresses, i. e. to perfectly anneal the glass, itis necessary 'to subject the glass article to a predetermined rate ofheating andvcooling, depending upon the nature of the article and thetemperature at any given time of the annealing process or degree ofpassage through the mule. These temperatures may only be allowed to varywithin very narrow permissible limits, say of i5 deg. C. It will beobvious to anyone acquainted with thefiring of gaseous or liquid fuelsemployed in modern leer prac` tice that no such regulatio'nis possible,and such being the case, perfectI annealing is not possible.

"It has been thought for some time that electric heating would beamenable to the' desired degree of temperature control to giveperfectannealing and a horizontal mufile leer has been built in which all ofthe heating has been accomplished by means of batteries of electricalresistances, most of which are placed. inside the Inutile next to thevertical walls. In principle, this leer is the same as the fuel firedleer just described, except that the necessary heat, instead of beingsupplied by the combustion of fuel -outside of the mule, is supplied bypassingv an electric current through batteries or sets of metallicresistors, most of which are located -inside the Inutile. But unlike thefuel fired leer, the amount and position of the energy supplied in theelectrically heated leer is subject to fine automatic control. This isaccomplished by inserting a thermocouple through the center of the roofof the muffle in the locality heated by the battery of resistors whichit is desired to regulate. This thermocouple comes within a few inchesof the top of the glass articles. The electro, motive force ofthethermocouple is used to actuate a chain of electric control apparatusof any suitable design, which controls the current passing through thebattery of resistors in question so as to maintain a constanttemperature of the thermocouple. In this way it has been possible tomaintain the temperature of thermocouples placed about 4 feet apartwithin i5 deg. C. of a predetermined temperature.

But the current consumption of such a leer has been'found to beexcessive, and the annealing not yet as perfectly under control as wasto be expectedvfrom the close control of the temperature of` thethermocouples.

I have attached thermocouples to a botv tle passing through such a leer,and have found that the actual temperature of the glass is quitedifferent from the temperatures recorded by the thermocouples insertedthrough the roof to Within a -fewinches of the glass articles. Thediscrepancy was most noteworthy in the receiving end of the leer wherethe bottles heated up more slowly the relative transparency of glass towave lengths of the visible spectrum concernedin transmitting heatenergy b v radiation from the electric resistors, which are at a glowingred heat. It is desired that this heat should be eiciently transferredto the glass for heating it up to annealing temperature, but instead ofsuch being the case, this radiant energy passes completely through thealmostV transparent glass and is transposed into sensible heat on theinternal walls of the muffle back of the resistors and on the surface ofthe thermocouples. These latter, therefore, register temperaturesconsiderably higher than the true temperatures of the glass in theheating region of the leer; and the excessive temperature of the insideface of the muiiie results in high losses by radiation.

The most e'ective means inside the leer for transferring the heat energyfrom the resistors to the glass articles is the stray convectioncurrents caused by the risin of heated air in contact with the heateresistors and inside walls of the mulie and the corresponding fall ofcooler air through the glass articles, thus setting up a circulation ofair which transfers heat from the resistors to the glass articles bymeans of convection. It is obvious that this same condition will existwhether the mulile be heated internally by electric resistors or eX-ternally by fuel. But these convection currents are stray and accidentaland are not employed systematically to help accom'- plish the heattransfer work of the leer. In the portion of the electrically heatedleer devoted to cooling, the thermocouples do not record the truetemperature of the glass which tends to cool slowly for 'the same reasonthat it heated slowly, and the result of this is that more electriccurrent is admitted to the resistors in the cooling region than isreally necessary to maintain the desired time cooling curve of the glassarticles, and this current is sheer waste.

The object of my invention is to provide strong systematically effectedvertical convection currents within the leer which will cause anefficient transfer yof heat from the walls or resistors in the heatingregion to the glass articles, and from the latter to the walls in thecooling region; and these same convection currents sweeping stronglyover the glass articles and thermocouples in turn, will cause the latterto register the true tempera-ture of the glass and to control theelectric input accordingly. In this way I am able to closely control thetrue temperature of the glass, thus causing perfeet annealing and at thesame time to greatly decrease the electric input to the resistors byreducing the temperature of the inside of the mufile in the heatingportion and by reducing the electrical input in the cooling portion.

My invention also provides a means for combining the `use of fuel, andelectricity whereby advantage is taken of the cheapness of the formerand the ease of regulation of the latter.

Referring to the drawings:

Fig. 1 is a longitudinal section through the center line of leer.

Fig. 2 is a side elevation.

I`Fig. 3 is a section on the line A-A of Fig. 4 is a section on the lineB-B of Fig. l.

Fig. 5 is a plan view.

Fig. 6 is a section on the line C-C of Figs. 3 and 4.

Fig. 7 shows a section of a portion of an electrically heated leerembodying my invention.

Fig. 8 shows a modified form of electrically heated leer provided with afan or fans for circulating the convection currents.

In the drawings, l is a horizontally disposed tunnel or muiie, and 1 isa noneated extension thereof which permits the glass articles to cool toatmospheric temperature before being discharged. The muiile 1 iscomposed of a top wall or arched roof 2 made of so called cupped tile 2of fire clay or other suitable material, and formed with a plurality ofopenings 3; a side wall 4, the upper part of which is composed of cuppedtile 4 and base of fire brick 4; and a bottom wall 5 composed of cuppedtile 5. Ordinary flat shapes could be substituted for the cupped tile,but the latter are chosen because it is desired to make the walls-of themulile highly conductive to heat.

6 is a pan-likelconveyor of any suitable design which moves slowlythrough the leer conveying the glass articles which are placed upon itfrom the receiving to the discharge end. Said conveyor is perforatedwith small holes to allow convectioh currents to pass vertically throughit and it runs on guides .8 whichare supported on I-beams 9, which, inturn, rest in the brick work. The conveyor )asses over wheels 10 towhich rotation is imparted by any suitable means. A door 11 closes thereceiving end when bottles are not being put in. A bafiie 12 is providedfor retarding the formation of currents of air in or out.

Electric heating elements or resistors 13 are placed along the interiorside walls of the Inutile 'and are supported on bracket bricks 14 and14". These resistors are arranged in sets or batteries, and forv eachbattery or set there is provided athermocouple 15. These latter areconnected with automatic electric control apparatus of any suitabledesign which so regulates the current to the several batteries or setsof resistors that the temperature reading of the thermocouple is keptpractically constant at the desired points for the proper annealing ofthe glass articles which are being conveyed through the muHle at aconstant rate of travel b the pan conveyor 6.

The mu e 1 is backed on both sides and top by partition tiles 16 made ofa refractory or semi-refractory material. These partition tiles arecomposed of partitions 16 and vertical passages 16". The verticalpassages 16I connect through horizontal ducts 17 with the interior ofthe muHle 1 at the bottom of the same and through the vertical ducts 3with the interior ofthe muHle at the top center of the roof. Thevertical passages 16" give a continuous connection between the ducts 3and the ducts 17. The continuity of the tiles, themselves, is broken forpurely structural reasons at the edge of the roof, and the thrust of theroof arch is taken up by skew backs 18, 19, and I-beams 20 and 21 andtie rods 22.

The partition tiles, in turn, are backed up bv the wall 23 composed ofcup tile 23',

which, as above, are used to make the wall highly conducting to heat,and the said tile are composed of some suitable refractory material.

Walls 23 and 5 on the bottom of the muHle are backed by a system of Hues24. These Hues on the bottom are backed on the lower side by anotherwall 25 composed of cup tile supported on I-beams 26. The Hues 24 arebacked on the side and top by the tire brick wall 27 and insulatingbrick wall The system of Hues 24 entirely surrounds the Inutile from endto end, the individual Hues in said system being differentiated by theexponents a to j, inclusive.

At the receiving end this Hue system is connected with the fire box 29,which is heated by an oil or gas burner 30 through the vertical Hue 24,This latter conducts the heated gases to the top of the muHle and thencealong the top through the opening 24b against a baille 31, whichdefliects gases downwardly through the Hue 24, thence across the bottomagainst a baffle 32, thence around through the Hue 24' across the bottomo the muHle outwardly, thence upwardly through the Hue 24 along the topof the mutlie against a baHle 31', thence down through the Hue 248across the bottom toward the center through the Hue 24h outwardlythrough the Hue 24i and upwardly through the Hue 241, etc. until thegases of combustion finally pass out through the Hues 33 and 33 into thestack flues 34 and thence up the stack 35.

A fan 36 is connected through a pipe 37 controlled by a damper 38 to theHue 24j just above the point where the latter enters into the stack Hue34. Dampers 39, 40 are arranged in the Hues 33, 33 and a damper 41 isarranged in Hue 241. If it is desired to have all of the gases ofcombustion enter damper 38, and this will circulate around through theHue system 24 and out through a pipe 42. Thus, the discharge portion ofthe muHle can be either heated by the gases of combustion or cooled byair at will, or, by adjusting the necessary dampers, any desiredcombination of these two effects may be had.

In operation of the leer, the fuel burner in the tire box 29 and theplacing of the dampers 39, 40, 41, 38 are so adjusted that 'the'temperature readings on the thermocouples 15 are slightly below thetemperatures desired for perfect annealin The fuel fired and theadjustment of ampers are then kept constant. The small additional amountof temperature necessary is then supplied by electric current admittedto the resistors 13 by the automatic electric control referred to above,but not shown, which also takes care of all the normal variations inoperation and automatically maintains a constant reading on thethermocouples 15 with the use of a very small amount of electriccurrent. This quantity of electric current is necessarily very smallbecause the principal heat energy required by the leer is supplied bythe fuel burned in fire box 29, and only a small amount of it b theelectric current, but the quantity of t e latter is sufficient to effectthe automatic control of the temperature necessary for perfectannealing.

^ The combined use of the fuel and electricity, with the manifestadvantage of the economy of the former and the delicatead-v justabilityof the latter, is made possible by the construction of the walls of themuHle. Heat from the resistors 13 and from the gases in Hues 24 passesthrough the highly conductive walls 2 and 4 and 23. respectively, intothe partition tile 16, whence, by reason of the large surface exposed bythe partitions, it is `converted into sensible heat in the air in theHues 16". On the other hand, as has been shown above, the

having a higher temperature than the air surrounding the glass bottles,and this promotes an active circulation of air up through the flues 16down through 3, thence down through the glass articles, through theholes 7 in the pan conveyor 6 and around its edges, thence over wall 5,where air begins to be heated, through flue 17 and up through the iues16 again.

This active and systematic circulation of convection currents insuresthat the thermocouples l5 will register' the true temperature of theglass, or nearly so, because the glass, due to these currents, will tendquickly to become of the same temperature as its surroundings.

Another great advantage is that, as the heat flow is in oppositedirections toward the center of the partition tile inwardly from thegases and outwardly from the resistors, no heat from the latter canpossibly escape through the outside walls of the leer and be dissipatedto the atmosphere, thusv eliminating a great source of loss of heatenergy in electric leers as at present constructed.

In the cooling portion of the leer where heat is being extracted fromthe glass articles, the circulation of convection currents is oppositeto that just described, i. e., upward through the articles and downwardthrough the flues 16".

The principle of heating as above described consists in imparting heatfrom both sides to an enclosed air current surrounding a muiiie, whichheat is transferred to the articles in the interior of the muie byconvection currents induced by the temperature difference between theVarticles being heated (or cooled) and the surrounding air current andthe flu'es which enclose it; and such a principle of heating makespossible the simultaneous use of heating by resistors within the muieand by hot gases of combustion from without.

It is obvious that many variations of the above construction may beemployed without departing from the spirit of my invention. For example,the heating by gases of combustion can be omitted entirely and all theheating done by the electricity, or the latter can be omitted and allheating done by the former. However, an important advantage in the wayof economy resides in the cornbination of the two methods of heating.

A type of electrically heated/leer is shown in Fig. 7. In this form ofthe device the walls are preferably constructed of fire brick A backedby hollow partition tile B, the latter having vertically extendingpassageways. These passageways at the bottom connect with the inside ofthe mule through ports C. The roof of the `leer is made of standardarched brick D backed by partition tile E. The passagewa s in thepartition tile E communicate wit the interior of the muie through portsF.

when the latter is being heated, ecause the y glass is an inefficientabsorber of radiant energy, and this difference of temperature willcause an active circulation in the direction ofthe solid arrows, whichin turn will promote transfer of heat to the bottles and reduce transferto the outside through the walls. i

When heat is to be abstracted from the glass the direction of thecurrents is reversed, as shown by the dotted arrows.

Another form of electrically heated leer embodying my invention isillustrated in Fig. 8. In this form the roof is made straight and theinner course of cupped tile has been omitted therefrom. The side wallsof the muie include a course of cupped tile G backed by a hollow tile H.The vertical passageways in the hollow tile communicate with the bottomof the muiie through ports I, and at their upper ends these passagewayscommunicate with passageways in a course of hollow tile J, which latterare laid upon T-bars K. At intervals the hollow tile J are provided withports L opening into the interior of the muile at the top thereof. Thecirculation of convection currents will be similar to that indicated inFig. 7.

In this form I also show near the front end of the Inutile one or morepropeller fans M suspended from drive shafts N extending through theroof of the mule on the middle line of the same. to aid the circulationof convection currents in certain cases. As the temperature gradientbetween the glass articles in the leer and the walls of the muiie4decreases the natural circulation of the currents will decreaseaccordingly. In such cases the circulation may be aided by the use ofthese fans.

The term muflie, as used herein, is intended to apply to a tunnel heatedinteriorly, as in the case of an electrically heated leer, as well as toa tunnel heated ex teriorly, as in the case of a gas heated leer.

While the present leer or furnace is primarily intended for annealingglass articles, it is capable of use for heating or annealing variousother articles, as, for example, heat treating steel. Y

Having thus described my invention, what I claim and desire to secure byLetters Patent is 1, The method of transferring heat to, or abstractingheat from, glass articles in an annealing leer which consists in causinga circulation of convection currents in the These fans are used Vrior ofthe mu e.

2. The method of transferring heat to, or abstracting heat from, glassarticles in an annealing leer which consists of forming enclosedpassageways within'the walls of the mule and connecting said passagewayswith the interior of the muille at the top and bottom of the latter andsubjecting the Walls to tem rature control, whereby to cause convectloncurrents to be circulated in the r uired direction over the glassarticles within the mulle.

3. The method of transferring heat to, or abstracting heat from, glassarticles in an annealing leer which consists in forming a lining for theside walls of the muffle with material of good thermal coductivity,arranging hollow tiles between the lining and shell of said walls,placing the passageways of the hollow tiles in communicationwith theinterior of the mule at the bottom and top of the latter and subjectingthe lining of the side walls to temperature control whereby to causeconvection currents to` be circulated inthe required direction over theglass articles within the muflle.

4. The method of transferring heat to, or abstracting heat from, glassarticles in an annealin leer which consists in forming the mu e of theleer with -side walls having vertically extending enclosed passagewa s,putting the .passageways within the wa s into communication with theinterior of the mule at the bottom of the latter, forming in the roof ofthe mullle enclosed passageways communicating with the passageways inthe side walls and putting the passageways in the roof intocornmunication with lthe interior of the muflle at the top of thelatter, and subjecting said walls to temperature control to causeconvection currents to be circulated in the reuired direction throu hthe interior of t e mule and throng the passageways within the walls androof.

5. The method of annealin lass articles in an annealing leer wliciconsists in forming the side walls of the mume with vertically extendinpassageways in communication at their` ower endswith the bottom of themume and openin into the to of the muflle through the roo thereof, an

appl ing heat to -o posits sides of the walls of t e mullle so t at air`within the passageways will be raised to a higher tem` perature than theair surroundin the glass articles within the where y convection currentswill be- )circulated over the glass articles and through saidpassageways.

6. A method of annealing glass articles in an annealing leer whichconsists in forming the walls of the muile with vertically extendingpassageways opening into the interior of the mufle lat the bottomthereof and communicating passa eways in the Iroof opening into the top0% the muflle, arrangin gas heated lues on the exterior of the wa ls andelectrically heated .means on the interior walls of the muiile wherebyair within the passageways will be heated from both sides, therebyraising the temperature to a point higher than the air surrounding theglass articles within the mufle for the purpose of causing convectioncurrents to be circulated over the glass articles and .through thepassageways.

7. A method of annealing glass in an annealing leer which consists informing enclosed vertical passageways within the side walls of themulle, connecting said passageways at the bottom with the bottom of themule, connecting said passageways at the top with the interior of themuflle through the roof` thereof, whereby the air within the passagewayswill be ali'ected by changes in the temperature of the surroundingwalls, thus setting up a circulation of convection currents over theglass articles.

8. A glass annealing leer comprising a mulle, enclosed passagewaysformed in the walls of the muilie and communicating with the interiorthereof, said passageways being so arranged as to receive heattransmitted from the 'walls of the muie so as to cause convectioncurrents to be circulated over the Y articles .within the muille.

9. A glass annealing leer comprising a mulle .having its side wallsformed with a lining of tile capable of readily conducting heat, hollowtile back of the lining having lvertically extending passageways, saidpassageways communicating with the interior of the mule at the bottomand with the top of the muflie through the roof thereof whereby thelining will transmit heat to the air within the passageways of thehollow tile and cause circulation of convection currents through themuflie and hollow tile.A

10. A glass annealing leercomprising a mule having its side walls formedof hollow tile with vertically extending passageways, a course ofheat-conducting tile forming a lining for the walls and ay course ofheat-conducting tile forming a shell for the walls, the passageways inthe hollow tile being in communication with the bottom and top of themuille whereby heat will be transmltted to the air in the passageways ofthe partition tile, thereby causing a circulation of convection currentsthrough the mule and passageways. l s

11. A glass annealing leer comprising a muiiie having its side wallsformed of hollow tile with vertically extending passageways, a course ofheat-conducting tile forming a lining for the walls and a course ofheat-conducting tile forming a shell for the walls, the passageways inthe hollow tile being in communication with the bottom and top of themuiiie, electrically controlled means for heating the lining of themuiiie and fuel fired means for heating the shell of the mufie wherebyheat will be imparted from both sides to air within the passageways,thus causing a circulation of convection currents through the interiorof the muie and passageways.

12. A yglass annealing leer comprising a Inutile havingits side wallsformed of hollow tile with vertically extending passageways, a liningand shell for said mulile formed of material capable of readilytransmitting heat, the passageways in the hollow tile being incommunication with the bottom and top of the Inuiile and means Jforheating the walls of the muiiie on opposite sides of the passagewayswhereby to set up a circulation of convection currents through saidpassageways and through the interior of the mu e.

13. A glass annealing leer comprising a muHe having its side wallsformed of hollow tile with vertically extending passageways, a liningand shell encasing said hollow tile, a fire box for heating the mutie, asystem of iues connected with the tire box and extending in series fromend to end of the muile, said iues extending*` vertically on theexterior of the side walls across the top of the roof and beneath thefloor of the muie, and said passageways being in cornmunication with theinterior of the mule at the bottom and top of the latter.

14. A glass annealing leer comprising a muiiie having its side Wallsformed of hollow tile with vertically extending passageways, a liningand shell encasing said hollow tile, a fire box for heating the mufiie,a system of lues connected with the re box and extending in series fromend to end of the mulile, said lues extending vertically on the exteriorof the side walls across the top of the roof and beneath the floor ofthe muie, said vpassageways being in communication with the interior ofthe muie at the bottom and top of the latter, and means for varying thepoint of outlet for the heated gases passing through said flue system.

15. A method of transmitting heat to, or

abstracting heat from, articles in an annealing leer which consists incausing a circulation of down or up currents over the articles in themule by the formation of passa ways for the air in the interior of thesi e walls of the muie, placing such passageways in communication withthe mule at the top and botom, heating the interior of the muiiie andsubjecting the air within the mulile to the action of a fan whereby ,toaid the natural circulation of the currents.

16. The method of annealing glass articles in an annealing leer whichconsists in forming the side walls of the muiiie with enclosedvertically extending passageways, placing such passageways at one end incommunication with the bottom ofthe muie and at the opposite end withthe top of the muffle and heating the interior of the muiileelectrically, so as to set up a circulation of convection currentsthrough said passageways and across the articles in the muiiie.

17. A method of annealing glass articles in an annealing leer whichconsists in forming the side walls of the muiie with enclosed verticallyextending passageways, placing such passageways at one end incommunication with the bottom of the muiiie and at the opposite end withthe top of the muiile and arranging electric heating elements within themuiie upon the side walls thereof, whereby convection currents will becirculated through said passageways and across the articles in themuiiie.

18. A glass annealing leer comprising a muiiie having its side wallsformed with enclosed vertically extending passageways connected at oneend with the bottom of the muiiie and at the other end with the top ofthe muiiie, electric heating elements arranged within the muiiie on theside walls thereof and thermo-couples disposed within the muiileadjacent the glass articles undergoing annealing, whereby the temerature gradient between the articles un ergoing l treatment and thewalls of the mufiie will be reduced by the circulation of convectioncurrents.

19. A furnace for heat treating purposes comprising a muiile having itsside walls formed with enclosed passageways opening into the muitle atthe top and bottom and means for causing currents to be circulatedthrough said passageways and over the articles undergoing treatment.

20. A furnace for heat treating urposes comprising a muiiie having itsside walls formed with enclosed passa ways opening into the mule at thetop an bottom, and a fan within the muiile for circulatin currentsthrough said passageways an over the articles undergoing treatment.

21. A furnace for heat treating purposes comprising a mule, electricheating means within the muie, the walls of said mule being providedwith vertically extending assageways opening at one end into the ttom ofthe muie and at the opposite end `into the top of the mume, saidpassageways 22. A furnace for heat treating purposes comprising a lnulehaving vertically eX- tending passageways in its side Walls Opening atone end into the bottom of the mule and at the opposite end into the topof the mufle, electric heating means Within the Inule adjacent the Wallswhich contain the passageways, thermo-couples within the mule adjacentthe articles undergoing treatment and means for circulating currentsthrough said passageways and over the articles undergoing treatment.

HUBERT D.

